Its a mystery

Welcome all,

I have an 81XJ650 Maxim. I have done a full tear down on the motor and the carburetor. Engine has been rebuilt. Compression test is within specs. The the timing dots are spot on with #1 cylinder. The shims haver all been triple checked for correct spacing. The Fuse shave all been replaced with The switch blade type. The carburetor has been brought to the church of clean. Almost all new parts. Gaskets, Needles, all original #s double checked. Ultrasonic cleaned. Ever carb separated and thoroughly checked. I've used a guitar string to check every port. Air fuel mixture screws set at 2.5. Butterfly valves all synced with guitar string. Followed all guides on that. I just replaced the #1-4 coil. both coils have spark. everything ohm checked. I recently had slippage to the starter clutch. Cleaned out engine with Seafoam. This fixed the problem. Also the Starter has been taken apart and cleaned and polished. Nice and copper again. All ground point have been cleaned. Fuel currently setup with an accessory tank to do testing. Suction hose has been closed off for carbs. Battery voltage is good. Getting over 10v when cranking for start. So with all that I'm still not getting a start. It cranks but no ignition. I've double checked my Jets #';s are correct and all in the right spots. Starter fluid isn't even working. Also just tried with new fluid Using 92 octane. Really stuck here. Theoretically it should fire even rough but its not. Unless my timing is way off somehow. if the #1 piston is TDC and the dots match that. Shouldn't that be good for timing. I've never moved the timing Arrow mark so it should still be good in theory.

Please help. I'm totally stuck at this point.

 

Slacken the float bowl drain screws a little to make sure the bowls are full, they should be but check anyway. Just read again you have already tried starter fluid.

 

I have moist defiantly done that. I feel like maybe the fuel isnt spraying into the engine? the bowls always fill up and are level. within the 1-3mm spec.

 

Do you have spark? How are the plugs, I've had a bad plug before that would spark in free but wouldn't work in an engine. Would be unlikely all four would be bad but maybe fouled out from all the starting attempts?

 

Yes l was thinking that too. Try what jayrodoh says might just be fouled plugs.

 

This is a interesting post . how much over 10v ?

 

Ive replaced the plugs once already. Ive cleaned them also when fouled. Spark is good. Highly doubt all 4 wont spark.

 

I get between 10-11v depending on the charge of my battery. I know it has to be over 10v. I have also checked the voltage at the TCI connector while hitting the start button to make sure its holding over 10v. So far s good. I was getting a drain from a bad coil that was pulling a full volt. So my voltage is higher now that I fixed that. Any other ideas? Thanks all so far by the way. I have read these forums alot to get ideas.

 

voltage spark-good, valves compression -good. starter fluid should at least get you a cough --- this is a interesting post. It seems you've done everything people would suggest. worth following for the solution.

 

Im wondering about the pilot jet now, well maybe the passageway. The Jets themselves are pristine. Totally clean. But maybe there's blockage in the passages i cant see? any suggestions on how to check them or clean them out? I have ultrasonic cleaned the bowls but not the full carb them selves. maybe this is the issue? I've always had to use the choke when i had it running for a very small period. I mean full blast choke. which means the pilot is getting bypassed. maybe this could be it? wouldn't that even keep starter fluid from working?

 

flinging stuff now.. are your coils connected to the correct elec.couplings,
700 -yellow coup. left coil 1,4 white cup. right coil 2,3.
you would still get spark and voltage if opposite.

 

If the jet in the bowl well is not clear you will have a hard time starting/idling. That jet is the hardest part of the carbs to clean.

 

Yes the coils are in the correct positions. It not that. Wish if would be so simple.

 

The bowls themselves are completely cleaned. Ultrasonic cleaned. I have also heated them up and sprayed carb cleaner in them boiled the carb cleaner and cleared out the holes. I can see light through them and have had carb cleaner sprayed through and watched it come out. Its not the bowls.

 

Are the air jets in the correct positions?


Were the fuel levels adjusted by the wet-set method?
Setting the fuel levels


EDIT:
I reread yourfirst post.You stated that starter fluid isn't working.
Are the plugs new, or are they the ones you had in the engine before the rebuild?

 

Air Jets are in the right spot. I've read these forums so many times looking for an answer. Fuel levels are correct. On and off the bike. Which plugs are you referring to? I have checked all the jets. I can see through them all. I have replaced the Jets with the stock size. What else you got? I need something outside the box. I keep getting the typical responses. I'm about ready to buy a diffrent type of carbs. Ive heard Murraycarbs.com is a good option. Just another $600 i dont want to spend.

 

outside the box. Me, I would try to bump start, bypassing starter current draw. - all you need is a sign it wants to run.

 

You shouldn't have to spend anything on different carbs, if it won't fire on starter spray through the carb body then another set of carbs is not gonna fix it. Everyone of these I've put back together I just sprayed a little fluid in the intakes (no carbs attached) and they all popped to life for a second.

I don't have anything "out of the box" to suggest, 8 years and I don't think I've seen another thread quite like this.

You say you have spark, can you confirm how you are testing this? Do you have an inline tester to see if it is actually sparking while the plug is installed?

Can you confirm what was done during the "engine rebuild." Helps to know what was/wasn't done.

What are the compression numbers?

Hard to imagine the marks are off if all the dots line up and you followed the procedure for installing and resetting the cam chain tensioner. Even if it was off and you bent a valve or valves the compression numbers would show this.

IIRC the timing plate only goes on one way, worth a check.

 

How do the resistor caps and resistor plugs work, not together l assume?

 

Are the spark plug caps on the correct cylinders?

 

Is it possible to have the low tension wires to the coils in the wrong connectors?

 

Franz, this has been addressed. -- it's the no fire on starter fluid is the mystery.

 

Yes of course l forgot about that.

 

Hey thanks for the reply. I'm going to try starter fluid with the carbs off see if a get combustion. As far as spark goes ive tried all 4 cylinders with the spark plug out and set against the engine. I haven't done it in the chamber. Will the pressure really kill the spark? I can get an inline tester if need be but if i spray starter fluid into the intake and get combustion then i know the spark is good right? As far as the engine rebuild goes I tore it down so I could change out the chain guide. It was breaking off and leaving plastic debris in my oil. I never messed with the transmission gearing at all. I looked it all over and it all looked good. No bluing or chipping or cracks that i saw. I have the manual so followed the book plus videos I've watched and read the forums. I had the cylinders honed out and new piston rings installed. The compression was checked and came back good. The numbers escape me at the moment. I just know they were within limits. Had another bike mechanic verify it. I never moved the timing plate. Ive always left it as is but the marker and TDC match up. I even gauged each cylinder to make sure they were maxed at the top and match my markings.

Thanks again for the reply. Ill check back after i try the ignition in the inlet tonight.

 

Ive done all resistance tests. They are within spec.

 

and if you get a pop, then what is the next step? extremely flammable gas 3" from a low spark will pop.
you'll still have install carbs to problem solve.

 

One of the seasoned forum guys told me this and I never believed him until it happened. Granted it was a lawnmower but I went though that carb 5 times, plug sparked fine on the head but that thing wouldn't fire to save my life. Grabbed the plug out of my power washer and it fired up. Would be unlikely you have 4 bad plugs, maybe the wrong ones though?

Good luck, keep us posted. And if it does fire then you're back to looking at the carbs etc. again.

 

If you have a colour tune you can check what is happening inside the cylinders during engine cranking. Got to be ignition if the starter fluid doesn't ignite.

 

the color tune for diagnosis is a good idea.

 

They can work together. It changes the burn time a bit, and maybe has a harder time when plugs aren't clean, but for the most part makes no difference.

 

Cheers l didn't know that.

 

The spark plugs? New or old?
One of the failure modes is having spark at atmospheric pressure, but not while in the cylinder under compression. It'd be very unlikely that all four would have that fault, but not impossible.

I'm also curious about the condition of the plug wires. Even a few pinholes in the insulation can cause a no/weak spark condition due the to spark jumping to ground at the cylinder head.

 

He might be able to see spark jumping onto the head when it's dark.

 

#1 coil wires and coil brand new. Just got 2 days ago. I will check #2 when it gets dark. Thanks

 

Yes but it takes alotxout of the equation.

 

Spark plugs are relatively new. Never ridden with them. Just used for testing. Yes I have fouled them a few times but have torched off and cleaned them to get good spark again.i have good blue spark.

 

How does color tune help if carbs aren't on? I can see using it once I know I have spark. Put the carbsxon and can get ignition enough to see the coloring. Otherwise I'm using starting fluid which will give me the wrong coloring anyway.

 

It was only to see inside the cylinder if the spark is happening on the compression stroke. Strange how you have a spark and starting fluid is not igniting.

 

Well didn't pop to life but did catch fire in each cylinder. Well poped and then fire. So getting ignition to all 4. So that's good. It's something.

 

Ok so I held that starter button and sprayed and got engine start with starter fluid into intake. So we are good there. Of course now my starter clutch is slipping even with the Rotella T4 oil so that's a major setback. Looks like a teardown it will be. Least I have ignition so I can go back to looking at carburator. Thank you all for the assistance.

 

Did you try bump starting it? Starter clutch slipping is a bummer.

 

No carburetor isn't hooked up right now. Was trying to figure out starting issue.

 

I had this issue on another bike and it ended up being out of sync carbs. They looked good but we’re off enough to cause a problem.

 

Any followup on this? I think I'm having the same issue lol

 

It's the carbs. I took off the carbs amd sprayed stater fluid directly into the engine port and held the ignition. I tried all 4 ports and they all ignited so definitely issue with the carbs. Just so happens my starter clutch started slipping so had to do a full tear down. Always something.